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Chapter 22 Species and Their Formation Biology 101 Tri-County Technical College Pendleton, SC Biological Species Species are independent evolutionary units Used to use morphological concept to assign organisms to a species (Linnaeus) Biological species concept introduced by Ernst Mayr in 1940 Species are groups of actually or potentially interbreeding natural populations which are reproductively isolated from other such groups Species, cont. “Actually and potentially” assert that, even if some members of species are NOT in the same place (at same time) and hence unable to mate, they should NOT be placed in separate species if they are like to mate if they were together “Natural” is important because only in nature does exchange of genes affect evolutionary processes Species, cont. Interbreeding of two different species in captivity does NOT affect evolution Gene exchange is MAIN REASON why species are cohesive units Are some limitations to biological species concept Speciation often very gradual process Species, cont. If barrier divides one population into two, the daughter population may evolve independently long before they become reproductively incompatible May also become reproductively incompatible before they evolve any noticeable morphological differences Short chapter, there is no Student Self Assessment in any form for this chapter